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String of Pearls Galaxy (NGC 55)
irregular galaxy in Sculptor
NGC 55 is a nearby, edge-on galaxy in Sculptor, a bar-shaped, elongated system with a lopsided look. It is a member of the Sculptor Group and a favorite of southern observers.
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// Key facts
- Catalog
- NGC 55
- Type
- irregular galaxy
- Constellation
- Sculptor
- Size
- 32′ across
- Brightness
- Magnitude 7.9
- Distance
- about 7 million light-years
- Peak month (any location)
- Sep
- Typical prime months
- Jul to Dec
- Difficulty
- Advanced
- Filter
- No filter (broadband); a light-pollution filter is optional
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How to image String of Pearls Galaxy
- It is far south (dec -39), so it is low from the northern United States.
- At 32 arcminutes, 600 to 1,000 mm frames it.
- Autumn evenings are best, and a dark sky reveals its mottled disc.
Framing: what focal length?
The focal length at which NGC 55 spans about 60% of the long side of the sensor, leaving room around it. Treat it as a starting point; the right framing is a matter of taste.
| Sensor | Focal length |
|---|---|
| 1-inch sensor (13.2 mm) | about 850 mm |
| APS-C (23.5 mm) | about 1510 mm |
| Full frame (36 mm) | about 2320 mm |
How high does it climb from your latitude?
The highest point NGC 55 reaches in the sky. Above about 60° is excellent, 30° to 60° is workable, and under 30° you are looking through a lot of air.
| Latitude | Highest point | Rating |
|---|---|---|
| 55°N (Scotland, Alaska) | below horizon | Never rises |
| 45°N (Minneapolis, Milan) | 6° | Stays low |
| 35°N (Los Angeles, Tokyo) | 16° | Stays low |
| 25°N (Miami, Cairo) | 26° | Stays low |
| 35°S (Sydney, Santiago) | 86° | High in the sky |
Also worth imaging
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